The Likert scale is a powerful tool for quality of life assessment among patients after minimally invasive coronary surgery

Introduction
Health-related quality of life (QoL) is an acknowledged index of treatment effectiveness. There are several methods of its evaluation which are predisposed to different risk of bias.

Aim
To investigate the agreement between objective and subjective tools of QoL assessment in patients who underwent endoscopic atraumatic coronary artery bypass (EACAB) grafting.

Material and methods
This prospective observational study covered 705 consecutive patients who underwent EACAB between April 1998 and December 2010. Quality of life was assessed in a follow-up of 2132 ±1313 days among 482 subjects using the WHOQoL-BREF questionnaire as an objective tool and the Likert scale as a more subjective method.

Results
There was good agreement between a 5-step Likert scale and a 5-step BREF Q1 (‘overall quality of life’) and Q2 (‘general health’) with a concordance correlation coefficient of CCC = 0.64 (95% CI: 0.58–0.69) and CCC = 0.49 (95% CI: 0.43–0.55), respectively. There was also a statistically significant correlation between answers reported using the Likert scale and all domains of BREF: physical health (R = 0.54, p < 0.001), psychological health (R = 0.56, p < 0.001), social relationships (R = 0.45, p < 0.001) and environment (R = 0.56, p < 0.001).

Conclusions
The Likert scale is useful in QoL assessment in patients after minimally invasive coronary surgery. This simple and easy-to-use screening method may be used interchangeably with a more reliable but also more complex questionnaire tool.